基于物质点法三维金属体积成形的数值模拟研究

发布时间：2018-06-30 03:55

本文选题：金属体积成形 + 弹塑性大变形　；参考：《湘潭大学》2016年硕士论文

【摘要】：金属体积成形是目前加工金属零件的一种重要手段,其成形过程为大变形过程,涉及几何非线性和材料非线性问题,必须借助数值方法来求解。物质点法作为一种新型无网格数值模拟方法,它即可以克服有限元法网格畸变问题,同时也有效地避免了传统无网格法的计算量大、本质边界条件施加困难、质点影响域搜索费时等不足。本文将物质点法应用于三维金属体积成形问题的数值模拟研究,分别对自由镦粗和反向挤压两种金属体积成形过程进行了数值模拟研究,并与有限元法及传统无网格伽辽金法模拟结果进行了对比,探讨了物质点法在模拟金属体积成形过程的可行性和有效性。具体内容为:采用加权余量法推导了物质点法控制方程的弱形式及其离散格式,给出了物质点法的显式计算流程;结合金属弹塑性理论与物质点法建立了金属弹塑性物质点法求解格式;利用Fortran语言编写了相应的计算程序,通过算例验证了弹塑性物质点法和程序的正确性;从计算效率、计算精度以及不同离散质点数下的计算结果等方面将物质点法与有限元法、无网格伽辽金法进行了对比研究。结果表明物质点法的计算精度和效率与有限元法相当,而高于无网格伽辽金法,并且在质点数目发生改变时表现出了比无网格伽辽金法更高的稳定性。基于物质点法对金属坯料自由镦粗和反向挤压的三维金属体积成形过程进行了数值模拟研究。在自由镦粗的模拟中,分别对无摩擦接触及有摩擦接触等情况进行了仿真分析,并与实验、有限元法的结果进行了对比,结果吻合良好,表明了本文利用物质点法计算三维金属体积成形问题时的可行性和有效性。在反向挤压成形模拟中,分别对不同压下量时坯料变形流动规律以及等效应力和等效应变的变化规律进行研究,并与有限元法以及无网格伽辽金法进行了对比,结果表明,当压下量较小时,物质点法与有限元法均能较好地模拟成形过程,但当压下量较大时有限元网格产生了严重的畸变而导致计算终止,而物质点法计算不受影响,能一次完成整个过程的计算,并与无网格伽辽金法结果吻合,可见在模拟金属体积成形大变形问题时,物质点法相比于有限元法具有更大的优势。本文的研究为物质点法应用于其它金属体积成形过程的数值模拟研究提供一定的指导作用。
[Abstract]:Metal bulk forming is an important method for machining metal parts at present. Its forming process is a large deformation process, which involves geometric nonlinearity and material nonlinearity. It must be solved by numerical method. As a new meshless numerical simulation method, the material point method can not only overcome the mesh distortion problem of the finite element method, but also effectively avoid the complexity of the traditional meshless method and the difficulties imposed by the essential boundary conditions. Particle impact domain search time and other deficiencies. In this paper, the material point method is applied to the numerical simulation of three dimensional metal volume forming, and two kinds of metal volume forming processes, free upsetting and reverse extrusion, are numerically simulated, respectively. Compared with the finite element method and the traditional Galerkin meshless method, the feasibility and effectiveness of the material point method in simulating the metal bulk forming process are discussed. The main contents are as follows: the weak form and the discrete scheme of the control equation of the material point method are derived by using the weighted residual method, and the explicit calculation flow of the material point method is given. Combining the metal elastoplastic theory with the material point method, the solution format of the metal elastoplastic material point method is established, the corresponding calculation program is compiled by using Fortran language, and the correctness of the elastic-plastic material point method and the program is verified by an example. In terms of calculation accuracy and calculation results under different discrete particle numbers, the material point method is compared with the finite element method and the meshless Galerkin method. The results show that the computational accuracy and efficiency of the material point method are similar to that of the finite element method, but higher than that of the meshless Galerkin method, and it is more stable than the meshless Galerkin method when the particle number changes. Based on the material point method, the numerical simulation of three dimensional metal volume forming process of free upsetting and reverse extrusion of metal billet was carried out. In the simulation of free upsetting, the non-friction contact and the friction-free contact are simulated and analyzed, and the results of the finite element method are compared with the experimental results, and the results are in good agreement with each other. The feasibility and effectiveness of the material point method in the calculation of three-dimensional metal volume forming problem are demonstrated in this paper. In the simulation of reverse extrusion, the deformation flow law, equivalent stress and equivalent strain of the billet with different reduction are studied, and the results are compared with the finite element method and the Galerkin method without meshes. When the reduction is small, both the material point method and the finite element method can simulate the forming process well, but when the reduction is large, the finite element mesh has serious distortion, which leads to the termination of the calculation, but the material point method is not affected. The calculation of the whole process can be completed in one time, and the results are in agreement with the results of the meshless Galerkin method. It is shown that the material point method has more advantages than the finite element method in simulating the large deformation problem of metal bulk forming. The research in this paper provides some guidance for the application of material point method in the numerical simulation of other metal bulk forming processes.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG302

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